Volume limiting ventilating apparatus



ct. 17, 1967 F. M. BIRD ETAL VOLUME LIMITING VENTILATING APPARATUS Filed Deo. ll, 1964 Mm mthmmmtn. QMQZB mq@ a R m K U/ NN If m u United States Patent O 3,347,228 VOLUME LIMITING VENTHATING APPARATUS Forrest M. Bird, Airport Box 970, Palm Springs, Calif. 92262, and Henry L. Pohndorf, 1227 Brewster Drive, El Cerrito, Calif. 94530 Filed Dec. 11, 1964, Ser. No. 417,564 Claims. (Cl. 12S-145.8)

ABSTRACT OF THE DISCLOSURE Volume limiting Ventilating apparatus having main control valve means for controlling the flow of gas to the patient during the exhalation and inhalation phases and having a sentinel valve for measuring the thoracic expansion of the patient and for controlling the operation of the main control valve means.

This invention relates to volume limiting Ventilating apparatus, and more particularly to a volume limiting Ventilating apparatus in which thoracic volume is sensed.

In -the respiratory and Ventilating apparatus presently available, it has been difficult to ensure that the patient being Ventilated is properly ventilated. This is particularly true in patients undergoing intensive care and patients under pre-operative and post-operative management. It is also true 4of tracheotomized patients where cuffed, partially cuffed or uncued airway tubes are employed and through which variable airway leaks may readily occur. With such apparatus, it has also been diilicult to obtain the proper ventilation without danger of oVer-ination during periods of variable airway leaks, changing pulmonary compliance and variations in mid-position. There is, therefore, a need for a new and improved Ventilating apparatus.

In general, it is an object of the present invention to provide a Ventilating apparatus of the above character which overcomes the above named disadvantages and which provides positive means for delivering a volume of gas into the lungs of the patient being treated.

Another object of the invention is to provide an apparatus of the above character in which there is a maximum inspiratory positive pressure limit without danger of over-ination during periods of Variable airway leaks, and changing pulmonary compliance.

Another object of the invention is to provide an apparatus of the above Acharacter which can be readily adjusted to tit Various sized patients.

Another object of the invention is to provide an apparatus of the above character which can be readily placed on the patient.

Additional objects and features of the invention will appear from the following description in which the preferred embodiment is set forth in detail in conjunction with the accompanying drawings.

Referring to the drawings:

FIGURE 1 is a schematic representation of a ventilating apparatus incorporating the present invention.

FIGURE 2 is a cross-sectional View of a portion of the means for sensing the thoracic excursion of the patient being Ventilated.

In general, the Ventilating apparatus has an inhalation phase and `an exhalation phase in its operative cycle. It is provided with controller which has an outlet adapted to be connected to the airway of the patient and an inlet adapted to be connected to a source of gas under pressure. The controller is provided with `a flow passage which is formed in the controller for supplying gas from the inlet to the outlet. The controller is also provided with main control valve means movable between open and closed positions for controlling the iiow of gas ACC through the flow pas-sage and to the outlet. The main valve means in the inhalation phase is in an open position and permits gas to ow to the outlet and during the exhalation phase is closed and prevents the vow of gas to the outlet. Means is provided for connecting the outlet to the airway of the patient to be ventilated. The controller is also provided with means for control-ling the movement of the main valve between open and closed positions and includes means for measuring the thoracic excursion of the patient being ventilated for causing the main control valve to shift from an open position to a Closed position.

More particularly, as shown in the drawings, the ven-tilating apparatus consists of a controller 11 and a supply 12 of gas under pressure. The controller is connected to a patient adaptor 13 which is connected to the airway of the patient land which is also connected to an exhalation valve assembly 14.

The controller 11 consists of a case or housing 16. The case or housing 16 is formed Iby a main body 17 of suitable material such as metal which can be of any desired configuration as, for example, rectangular as shown. A pair of end covers or enclosures 18 and 19, formed of a suitable material such as plastic, are mounted on the -body 17 to provide enclosed chambers 21 and 22 disposed on opposite sides of the body 17. The chamber 21 can be identified as the atmospheric pres-sure chamber, whereas the chamber 22 can be identified as the positive pressure chamber. The chamber 21 is vented to 4atmosphere through an opening 23 provided in the cover 18. The opening 23 is covered by a i-lter 24 of a suitable material, such as porous metal.

The controller 11 is provided with an inlet 26 which is formed in the body 17. The inlet 26 is adapted to be connected to a source of gas under pressure with which the patient is to be ventilated. This source is indicated as being a gas supply tank 12 which is connected to the inlet 26 -by a conduit 28 through a pressure reducing regulator 29. The controller is also provided with an outlet 31 which is formed in the cover 19 and which is connected to the patient adaptor 13 as hereinafter described. The controller 11 is also provided with a ow passage 32 which is formed in the body 17 and which is directly connected to the inlet 26 and opens into the chamber 22 formed in the cover 19 and also communicates with the outlet 31 provided in the cover 19.

The controller 11 also includes main control Valve means 34 which is movable lbetween open and closed positions for controlling the ow of gas through the flow passage 32. The main control valve means 34 includes a slidable valve member 36 which is slidably mounted in the body 17. The valve member 36 is provided with a passage 37 which is adapted to be moved into and out of registration with the passage 32 by sliding movement of the valve member 36 within the body 17. The Valve member 36 is movable between open and closed positions by suitable means such as a rubber diaphragm 38 which has its outer margins secured to the body 17 and which has its inner margin secured to the valve member 36 as shown in FIGURE 1 of the drawings. The body 17 is provided with an annular recess 39 which, in conjunction with the diaphragm 38, form an `annular chamber 41 which is adapted to be placed in communication with the chamber 22 through a passage 42 provided in the body 17 The chamber 41 is also in continuous communication with the upstream side of the passage 32 through a passage 43 provided in the body 17.

In the controller 11 shown in the drawings, means is provided for adjustably biasing the valve member 36 in an open position and consists of a pair of permanent magnets 46 `and 47 mounted on screws 48 threaded into the side walls of the covers 18 and 19. Knurled knobs 49 are provided on the screws 48 to permit the screws and the magnets carried thereby to be adjusted longitudinally and axially towards and away from the Valve member 36. Means is carried by the opposite ends of the Valve member which is adapted to be attracted by the magnets 46 and 47 and consist lofl circular plates 51 and 52, formed of suitable material such as steel, which are mounted on opposite ends of the Valve member 36 in general alignment with the magnets 46 and 47. It can be seen that by adjusting the position of the magnets 46 and 47 with respect to the plates 51 and 52, it is readily possible to adjust the amount of force required to move the valve member 36 in a longitudinal direction between the magnets 46land 47.

As hereinbefore explained, means is provided for connecting the outlet 31 of controller 11 to the patient adaptor 13. As shown in FIGURE l, such means consists of a flexible elongate tube 56 which is connected to a fitting 57 provided in the outlet31. The other end of the hose 56 is connected to a fitting 58 which is connected to the patient adaptor 13. The patient adaptor can be of any suitable type which makes connection with the patients airway. For example, it can take the form of a face mask or a tracheotomy tube which is shown schematically and is connected to the airway 61 of the patient and to the lungs 62 of the patient shown in broken lines in FIGURE l.

The patient adaptor 13 is also connected to an exhalation Valve assembly 14 which consists of a fitting 64 which is provided with an exhalation opening 66 andr which is normally retained in a closed position by a valve member 67. The Valve member is engaged by a Valve stem 68 which is slidably mounted within the fitting 64. The Valve member 67 is yieldably urged towards a closed position by a spring 69. The V-alve stern 68 is yieldably urged away from the Valve member 67 by a spring 71 and permits the Valve member 67 to open during the exhalation phase. Additional means is also provided for yieldably retaining the Valve member 67 in a closed position during the inhalation phase of the Ventilating apparatus and consists of a diaphragm 72 which is mounted within the fitting and engages the valve stem 68. Means in the form of a fiexible tube 73 is provided `for supplying the positive pressure from the conduit 74 iny the chamber 22 to the diaphragm 72. This pressure on the diaphragm 72 is greater than in chamber .22 because the flow passage into the conduit 74 :is larger than the size of the orifice 32a from the flow passage 32 into the -chamber 22. The fitting 64 is provided with an exhalation outlet 76 which is adapted to discharge the gases passing through the opening 66 when the Valve member 67 is moved to an open position during exhalation.

Means is provided for controlling the movement of the main control valve between open and closed positions. Such means includes means for measuring the thoracic excursion of the patient being Ventilated for causing the main control Valve to shift from an open to a closed position. This means consists of a diaphragm-operated Valve assembly 81 which is mounted on the case 16. The valve assembly 81 consists of a plunger rod 82 which is slidably mounted in a fitting 83 mounted in the body 17 and is also slidably mounted in the body 17. The plunger rod 82 is movable between open and closed positions. In thefclosed position, it occludes the passage 42, whereas in an open position, the passage 42 is in communication with the chamber 41. Means is provided for yieldably urging the plunger rod `82 into an open position and consists of a spring 84 mounted axially of the rod 82 and disposed in a well 8S provided in the fitting 83.

Means is provided for shifting the Valve member 82 between open and closed positions and consists of a flexible diaphragm 86, the outer margin of which is retained between circular cupped members 87 and 88 which are fastened together at their outer margins and which are supported by the tting 83. The inner margin of the diaplunger rod 82. The rear back side of the diaphragm 86 is exposed to the atmosphere through openings 90 provided in the member 88. The other side of the diaphragmv is in communication with a passage 92 in a fitting 91 mounted on the member 87. The passage 92 is connected by tubing 93 to the chamber 22 formed in the case16. The passage 92 is also connected to a sentinel valve 96 by suitable means such as flexible tubing 97.

The sentinel valve 96 consists of a Valve body 101 which is provided with a cylindrical bore 102. A shuttle valve 103 is mounted in the bore and is provided-with lands 103e and 103i). Means is provided for yieldably urging the shuttle valve 103 to oneextreme position (its first closed position) and consists of a spring 104 mounted on the shuttle Valve and seated within the body 101. The Valve body 101 is provided with a sighting opening 106 and an exhaust port 107. The shuttle valve 103 is provided with an additional index portion 103e` which can be colored an appropriate color suchas red and which is Visible through the sighting opening 106 for a purpose hereinafter described. In the first closed position as seen in FIGURE 2, it can be seen that the land 10313 occludes the passage 108 provided in the Valve body 101v extending at right angles to the bore 102.

Means is provided for securing the sentinel valve 96 so that it circumscribes the thoracic cage so that it will sense excursions in the thoracic cage of the patient being Ventilated. As shown in the drawings, such means consists of a suitable non-extensible elongate element adapted to be fitted around the thoracic cage of the patient being Ventilated. This element consists of a bead chain 111 which is provided with a connector 112 whereby the length of the chain can be adjusted to a snug fit about the thoracic cage of the patient to be Ventilated. A volume control Vernier 113 is provided for Iadjusting the length of the chain 111 and consists of a member 1'14 which has one end secured to the chain 111 and a member 11.6 which is threaded into the member 114 and which is also connected to another section of the chain 1'11. The member 116 is provided with an index line 117. The chain 111 is connected to the shuttle valve 103 by a fitting 118.

Means is provided for preventing the fitting 1118 orthev shuttle Valve from `pinching the skin of the patient during breathing and consists of a cylindrical member 121 formed of a suitable material such as plastic and which is mounted over the chain and has one end disposed in the.

Vicinity of the fitting 118. The cylindrical member 121 is of a diameter substantially greater than the diameter of the sentinel valve so that the shuttle Valve will be posi-v ratus. The sentinel valve 96 is mounted on the patient by placing the chain 111 aroundthe body so that itcircumscribes a thoracic circumference at any desired level or position on the body as, for, example, as shown in FIG- URE l of the drawings. The chain is properly adjusted or, in other words, the sentinel Valve 96 is properly rigged when the index line 117 of the Volume control Vernier 113 is just visible yand the red index portion 103C is barely visible through the opening 106 provided in the Valve body 101 during the post-expiratory pause.

The patient adaptor 13 can then be connected to the airway of the patient. Let it now be assumed that gas under pressure is supplied to the passage 32 from the source 27. When this occurs, Igas will' flow through the passage 32 and through the hole 37 in the Valve member 36 into the positive pressure chamber 22 through the tube 56 to the patient adaptor 13 and to the patient. At

the Sametime, the gasunder slightly higher pressure is supplied t'o lthe tube 73 to retain the exhalation valve member 67 in a closed position. Gas under pressure is also supplied through the tube 93, through the passage 92 and through the tube 97 to the sentinel valve 96. With the sentinel valve rigged as hereinbefore described with the red indicating portion 103 visible in the opening 106, the land 103b has been moved to the right to open the passage 108 so that gas passing through the tube 97 and through the passage 108 is exhausted to the atmosphere through the opening 107 provided in the valve body 101. The plunger rod 82 is spring-loaded by the spring 84 so that it remains in an outward or valve-open position as long as the gas passing through the passage 92 is exhausted through the port 107 provided in the sentinel valve 96. The means for shifting the plunger rod 82 to the closed position normally is set to operate below the pressure required to urge the valve member 36 to a closed position, as for example, 17 mm. of Hg. The controller 11, therefore, remains in an inspiratory phase and air is continued to be supplied to the patient airway to cause expansion of the lungs and the thoracic or upper abdominal dimension of the patient.

As expansion occurs, the shuttle valve 103 is shifted to the right as viewed in FIGURE 2 by the chain 111 until the land 10311 occludes the passage 108 to prevent any air from passage 108 from being exhausted through the port 107 of the sentinel valve. This causes the 4controller 11 to be cycled to its exhalation phase by causing a positive pressure to be applied to the upper side of the diaphragm 86 to cause the spring 84 to be compressed and to move the plunger rod 82 into a position so that it occludes the passage 42. As soon as the passage 42 is occluded, pressure builds up in the chamber 41 because of gas supplied to the chamber 41 through the passage 43. This causes the valve member 36 of the main control valve 34 to be shifted to the left as viewed in FIGURE l to occlude the passage 32 and to prevent any further air or gas to be supplied from the inlet to the outlet of the controller. As soon as the gas ceases flowing through the outlet, the positive pressure within the chamber 22 and the patient airway 61 and in the tube 73 and under the diaphragm 72 is caused to equalize thereby permitting the spring 71 to retract the valve stem 68 and the exhalation valve 67 to open as the patient exhales. The exhaled gases are discharged through the opening 66 and the outlet 76.

When exhalation by the patient is substantially complete, the sentinel valve 96 senses the decrease in the thoracic dimension and the shuttle valve -3 shifts as viewed in FIGURE 2 so that the land 103a no longer occludes the passage 108. As soon as this occurs, the pressure above the diaphragm 86 is substantially reduced to permit the spring 84 to return the plunger rod 82 to its normally open position. As soon as this occurs, the pressure is reduced in the chamber 41 and the valve member 36 returns to the normally open position under the force of magnet 47 and gas again flows through the passage 32 to start another respiratory cycle. The magnet 46 can hold the valve member 36 in a closed position -until the patient drains chamber 22 slightly so that atmospheric gas in chamber 21 urges diaphragm 38 and valve member 36 to the right as viewed in FIGURE 1 to an open position to allow a post expiratory pause.

From the foregoing, it can be seen that the sentinel valve has three different positions; one, a first closed position, second, an open position and third, a second closed position. In the event the chain 111 should break, the sentinel valve 96 will move to its first closed position in which the land 103b occludes the passage 108. However, in such event, the positive pressure within the chamber 22 will increase and this positive pressure will be supplied to the diaphragm 86 and to the airway of the patient so that the patient will receive therapy ventilation up to the normal pressure e.g. 17 mm. of Hg when the plunger rod 82 moves to its closed position. When the positive pressure delivered to the diaphragm 3S through passage 43 reaches a predetermined pressure which is determined by the positioning of the magnets 46 and 47, the valve member 36 is shifted to the left as viewed in FIGURE l which stops the inhalation phase in the manner hereinbefore described. The exhalation phase is accomplished in the same manner as hereinbefore described. Thus, it can be seen that the Ventilating apparatus is failsafe and will still adequately ventilate a patient even though the chain 111 should fail.

The magnets 46 and 47 serve as means for adjusting the peak or maximum pressure for Ventilating the patient up to 90 mm. of Hg at which the valve member 36 is moved from an open to a closed position by pressure on the diaphragm 38. It can be seen that by adjusting the longitudinal position of the magnets 46 and 47, the force required for moving the slidable valve member 36 from an open to a closed position can be readily adjusted. This peak pressure is set so that it is higher than that required to normally ventilate the patient but not so high as to be dangerous to the` patient. In addition, it is normally set at a pressure above that for which the plunger rod 82 is normally operated.

The fail-safe feature can be made to switch the ventilating apparatus between an inhalation phase to an exhalation phase at any desired pressure limit adjusted up to the peak pressure of 90 mm. Hg made available principally through adjustment of the position of the magnet 47 by changing the biasing pressure moving the plunger rod 82 to a normally open position. This is set at a safe level to prevent over ventilation of the patient.

When the sentinel valve 96 is moved to its open position as hereinbefore described, the positive pressure which can be applied to ventilate the patient can be any preselected pressure up to the maximum or peak pressure of 90 mm. of Hg as, for example, a maximum of 40 mm. of Hg. When the plunger rod 82 is set to operate at 17 mm. of Hg, any pressure from 17-90 mm. of Hg is available to satisfy the volume requirements of the patient.

'From the foregoing, it can be seen that the sentinel valve 96 slaves the Ventilating apparatus to changes in thoracic or upper abdominal dimension of the patient. It has been found that Aregardless of how frozen the thoracic cage may be, by secondary or pathological conditions, a movable dimension is present, usually at the diaphragmatic margins. It has been found that after the sentinel valve is properly adjusted, the patient is unaware of its presence as spontaneous ventilation is completely unimpaired. The sentinel valve serves as means for sensing the size of the thoracic cage and thereby serves as means for positively limiting the volume to which the thoracic cage can be expanded. Thus, there is no danger of high pressure over-inflation when functional residual capacity is increased during therapy. In addition, there is no failure to deliver preset volumes when variable airway leaks are present.

It is apparent from the foregoing that there is provided a new and improved Ventilating apparatus for delivering air to the airway of the patient with great safety and at the same time providing very positive means for limiting the volume.

We claim:

1. In a Ventilating apparatus having an inhalation phase and an exhalation phase in its operative cycle, ventilating apparatus comprising a controller having an outlet adapted to be connected to the airway of the patient and an inlet adapted to be connected to a source of gas under pressure, a ow passage formed in said controller for supplying gas from the inlet to the outlet, main control valve means mounted in said controller and movable between open and closed positions for controlling the ow of gas through said ow passage, said main control valve means during the inhalation phase being in an open position and permitting gas to ow from the inlet to the outlet and during the exhalation phase being closed to prevent the owof gas from the inlet to the outlet, means for connecting the outlet to the airway of a patient to be venilated, and means for controlling the movement of said `main control valve means between open and closed positions, said last named means including means for measuring the thoracic excursion of the patient being ventilated and for causing said main control valve means to shift from an open position to a closed position when a predetermined thoracic excursion is reached, said last named means also including a sentinel Valve connected to said means for measuring the thoracic expansion and movable between iirst and second positions as the patient exhales and inhales, means for supplying gas under pressure to the sentinel valve, said sentinel Valve being constructed so that in the first position the gas supplied thereto is exhausted to the atmosphere and in the second posi-` tion the gas supplied thereto is prevented from escaping to the atmosphere and means for operating said lmain control Valve means in response to operation of said sentinel valve.

2. A Ventilating apparatus as in claim 1 wherein said means for measuring the thoracic excursion of the patient includes non-extensible means encircling the thorax of the patient and securing the sentinel valve to the patient.`

3. A Ventilating apparatus as in claim 1 wherein said sentinel valve has iirst and second `closed positions and an open position.

4. Avventilating apparatus as in claim 1 wherein said means for operating said main control valve means in response to operation of said sentinel valve includes a valve member, a diaphragm carried by the Valve member,

means for supplying the gas under pressure from the outi let to one side of the diaphragm, and wherein the means for supplying gas under pressure to the sentinel valve is connected to said one side of the diaphragm.

5. In a Ventilating apparatus having an inhalation phase and an exhalation phase in its operative cycle, a controller having an outlet adapted to be connected to the airway of the patient and an inlet adapted to be connected to a source of gas under pressure, a body disposed in the controller, a iiow passage formed in said body for supplying gas from the inlet to the outlet, main control valve means mounted in said body and movable between open and closed positions for controlling the ow of gas through said ow passage in said body, said main control valve means also including a diaphragm and means for supplying gas from the inlet to one side of the diaphragm and means for bleeding oi air from the diaphragm to the outlet, said main control valve means in the inhalation phase being in an open position and permitting gas to flow from the inlet to the outlet and in the exhalation phase being closed to prevent the tlow of gas from the inlet to the outlet, means for connecting the outlet to the airway of the patient to be ventilated, and means for controlling the movement of said main control valve means between open and closed positions by measuring the thoracic expansion of the patient being ventilated, said last named means including a valve member movable into a position to occlude the passage from one side of said diaphragm to said outlet, additional diaphragm means connected to said last named valve member, means supplying gas from the outlet to one side of the additional diaphragm means, a sentinel valve movable between open and closed positions, means for securing the sentinel valve about the thoracic cage of the patient so that the sentinel valve is moved between said open and closed positions as the patient inhales and exhales, and means for supplying air under pressure from one side of the additional diaphragm means `to the sentinel valve, said sentinel valve being constructed so that in an open position the air supplied thereto is exhausted to the atmosphere and in a closed position the air supplied thereto is prevented from escaping whereby the additional di` aphragm means causes movement of said valve member to occlude said passage.

6, A Ventilating apparatus as in claim 5 wherein the sentinel valve includes a valve body and a shuttle Valvev `ing, said shuttle valve having iirst and second lands,

means mounted on the body for yieldably urging the shuttle valve into a closed position kin which said second land prevents the flow of gas from said inlet port to said` outlet port, said means for securing the sentinel valve to the patient being adjusted so that the sentinel valve is iirst moved into an open position in which the shuttle valve is shifted so that said lands are out of engagement with said inlet and outlet ports and the inlet and outlet ports are in communication to permit the flow of gas therethrough during the inhalation phase and in which the iirst land is vmoved into registration with the inlet and outlet ports to prevent the flow of, gas from the inlet port to the outlet port at the termination of the inhalation phase and the commencement of the exhalation phase.

7. A Ventilating apparatus as in claim 6 wherein said Valve body is provided with a sighting opening and wherein said shuttle valve is provided with means visible through said sighting opening to indicate when said second land occludes the ow of gas from said inlet port to the outlet port of the valve body.

8. A Ventilating apparatus as in claim 7 wherein said means for securing the sentinel valve about the thoracic cage of the patient includes Vernier adjustment means to permit adjustment of the sentinel valve so that the indicator of the shuttle valve is disposed in said sighting opening in the valve body.

9. In a Ventilating apparatus having an inhalation` phase and an exhalation phase in its operative cycle, a controller having an outlet adapted to be connected to the airway of the patient and an inlet adapted to be conneeted to a source of gas under pressure, a body disposed in the controller, a flow passage formed in said body for supplying gas from the inlet to the outlet, main control Valve means mounted in said body and movable .between open and closed positions for controlling the flow of gas through said ow passage in said body, said main valve control means including a valve member slidably mounted in said body and adapted to be moved into and out of engagement with said ow passage to control the ow of v gas through said flow passage, a diaphragm having its inner margin secured to said Valve member and its outer margin secured to the body, an additional iiowpassage in said body connected to said iirst named ow passage vfor supplying gas from said iirst named flow passage to the side of the diaphragm facing the body, a third ow passage in said body connecting the side of the diaphragm facing the body with the outlet, means yieldably biasing the Valve member towards an open position to permit the ow of gas from the inlet to the outlet in the inhalation phase, said diaphragm being capable of moving said valve member against the force of the yieldable means into a closed position to prevent the `tiow of gas fromthe inlet to the outlet during the exhalation phase, means for-connecting the outlet to the airway of the patient to be Ventilated, and means for controlling the movement of said main conrol valve between open and closed positions, said last named means including a valve member movable into a position to occlude said thirdpassage, means including a diaphragm connected to said last named Valve member and forming a chamber, means for supplying gas supplied to the outlet to said chamber, means for-sensing the thoracic expansion of the patient being ventilated, said last named means including a sentinel Valve movable between open and closed positions, means connecting said chamber to said sentinel Valve so that when said sentinel an open position during the inhalation phase and in a closed position the exhalation phase, said sentinel 2,071,215 2/1937 Peterson 128-28 McCann 128-208 Emerson 12S-30 Black 128-145.8

Franz 12S- 145.8 Bird et al 128-1458 RICHARD A. GAUDET, Primary Examiner.

10 K. L. HOWELL, Assistwnt Examiner. 

1. IN A VENTILATING APPARATUS HAVING AN INHALATION PHASE AND AN EXHALATION PAHSE IN ITS OPERATIVE CYCLE, VENTILATING APPARATUS COMPRISING A CONTROLLER HAVING AN OUTLET ADAPTED TO BE CONNECTED TO THE AIRWAY OF THE PATIENT AND AN INLET ADAPTED TO BE CONNECTED TO A SOURCE OF GAS UNDER PRESSURE, A FLOW PASSAGE FORMED IN SAID CONTROLLER FOR SUPPLYING GAS FROM THE INLET TO THE OUTLET, MAIN CONTROL VALVE MEANS MOUNTED IN SAID CONTROLLER AND MOVABLE BETWEEN OPEN AND CLOSED POSITIONS FOR CONTROLLING THE FLOW OF GAS THROUGH SAID FLOW PASSAGE, SAID MAIN CONTROL VALVE MEANS DURING THE INHALATION PHASE BEING IN AN OPEN POSITION AND PERMITTING GAS TO FLOW FROM THE INLET TO THE OUTLET AND DURING THE EXHALATION PHASE BEING CLOSED TO PREVENT THE FLOW OF GAS FROM THE INLET TO THE OUTLET, MEANS FOR CONNECTING THE OUTLET FOR CONTROLLING THE MOVEMENT OF VENILATED, AND MEANS FOR CONTROLLING THE MOVEMENT OF SAID MAIN CONTROL VALVE MEANS BETWEEN OPEN AND CLOSED POSITIONS, SAID LAST NAMED MEANS INCLUDING MEANS FOR MEASURING THE THORACIC EXCURSION OF THE PATIENT BEING VENTILATED AND FOR CAUSING SAID MAIN CONTROL VALVE MEANS TO 